Machine for manufacturing recessed plasterboard



Jan. 15, 1946. R. H. HuRo 2,392,923

MACHINE FOR MANUFACTURING RhcEssEn PLAsTERoARn Filed April 11, 1942 3 Sheets-Sheet 1 RW Nk@ R. H. HURD Jan. 1s, 194s.

MACHINEFOR MANUFACTURING RECESSED PLASTERBOARD Filed April 11, 1942 3 Sheets-Sheet 2 R. H. HURD Jan. l5, 1946.

MACHINE FOR MANUFACTURING RECESSED PLASTERBOARD Filed April 11, 1942 3 SbeetsP-Sheet 3 Patented Jan. l5, 1946 `MAGHINE FOR MANUFACTURING BECESBED PLASTEBBOARD Ralph H. Hurd, Clarendon Hills, lll., assigner to United States Gypsum Company, Chicago, Ill.,

a corporation of Illinois Application April il, 1942, Serial No. 438,578

claims.

Vto cover the Joint between the boards and without any projection being formed at the joint.

In using boards of this type, it is common practice. after the adhesive tape ig applied over the joint, to illl the recess and the lnterstices adjacent the edges of the tape with a suitable coinposition commonly known as a joint i'lller. 'I'his is a plastic composition and is very adhesive so that a smooth and unbroken surface can be made. The Joint filler hardens and sets to a rigid condition so that the recess formed by the adjacent depressed portions of the board is filled flush with the outer surface of the plesterboard and the wall presents a smooth and unbroken ap- Dearance.

In manufacturing Wallboard of this type. considerable difiiculty has been experienced in providing the depressed or recessed portion with a flat surface after the gypsum in the plasterboard has set. In ordinary practice the fabric covering of the plaster-:board is first offset or crimped by means of shouldered rollers so that a portion of the fabric strip adjacent the edge thereof is offset at least the depth of the recess. The wet gypsum slurry is then applied to the fabric and the edge of the fabric folded over the gypsum to form the edge of the board. A fabric backing is then applied on the wet board to which it is adhesively secured when the board dries. The vertical edge of the board may be left uncovered if desired, in which case the folding operation is unnecessary. However, this method has been more or less unsatisfactory for the reason that the combined action of the crimping operation on the fabric and the moisteningof the fabric by the wet gypsum causes the paper along the bottom of the recess to bow or arc inwardly so that the door of the recess is not perfectly fiat. 'l'hc gypsum then sets and the surface of the reduced portion remains distorted.

A further objection to prior methods is that, on account of improper crimping and the fact that, in passing through the master rolls. the fabric was not properly supported to conform to the offset o: the recess, the finished board tended to bulge outwardly adjacent the inner or crimped edge of the recess.

The present invention overcomes all of the above-noted objections to prior methods and machines and provides improved crimping devices and master rolls which co-operatively function to produce smooth fiat-surfaced plasterboards having marginal recesses in which the floors or depressed surfaces of the recesses are substantially ilat and parallel with the board surfaces.

It is an object of the present invention to provide means for crimping or creasing the fabric covering prior to the application of the wet gypsum thereto in such a manner that the surface of the entire board. including that portion which is reduced in thickness to form the recessed edge. will remain smooth and fiat throughout the entire process of manufacture of the board and after the board has been thoroughly dried.

A further object is to provide a board manufacturing machine including paper or fabric crimping devices, means for delivering moist gypsum to the paper strip. and master rolls for forming the plasterboard. in which the fabric is crimped and the manufacture of the board completed without putting any undue friction or frictional strain on the so-called crimped portion of the fabric.

A further object is the provision of a plasterboard manufacturing machine of the character described which will be cheap to manufacture. convenient in use. and will not easily get out of order. also in which the various elements are easily adjustable to board manufacturing requirements.

Further objects will be apparent from the specification and the appended claims.

In the drawings:

Fig. i is a fragmentary cross sectional view through a portion of a wall and illustrates the abutting recessed edges of the wallboard of this invention, the fabric tape and Joint filler com.- position forming a part of the finished wall being shown by dotted lines.

Fig. 2 is an enlarged fragmentary sectional perspective view of the recessed edge of one of the plasterboards shown in Fig. l.

Fig. 3 is a somewhat diagrammatic side eletration of a plasterboard manufacturing machine and illustrates one embodiment of the invention.

Fig. 4 is a top view of the fabric crimping p0rtion of the machine illustrated in Fig. 2 and illustrates the relative arrangement of the crimping units.

Fig. 5 is a transverse sectional view through one of the crimping units and is taken on a line substantially corresponding to line B-l of Fig. 4.

Fig. 6 is a right hand end view of the crimping unit shown in Fig. with the table and base shown in cross section.

F18. '7 is an enlarged fragmentary sectional view of the shoulder forming portion of the crimping rolls.

Fig. 8 is a front view of the master rolls and illustrates the interchangeable fabric-supporting ring and a filler ring for the unused ring groove.

Fig. 9 is a somewhat diagrammatic view of the master rolls and the scraper assembly used in connection therewith.

Fig. 10 is a plan view of the co-operating scraper blades for the lower master roll and the rings thereon.

Referring to the drawings in detail. the wall section illustrated in Fig 1 comprises plasterboards I which may be applied to a stud 2 in any well known manner. Marginal portions 3 along the adjacent edges of the boards are reduced in thickness as illustrated to provide a shallow depression or recess in the face of the wall along the joint. The outer sides of the boards are covered with a fabric I, usually paper, and this fabric may be folded around the edge of the board and overlapped as shown at 5. or the boards may have a raw edge if desired. A backing fabric 6 is provided which overlaps the folded portion E as shown. A fabric tape such, for instance. as a paper strip may be adhesively applied over` the joint, as indicated by dotted lines 1, and the recess and interstices thereof may be filled with a suitable joint filler E also shown by dotted lines.

An enlarged view of the recessed portion of one of the finished boards is shown in Fig. 2, in which the depth of the recess is somewhat exaggerated over ordinary practice for purposes of illustration. The board is reduced in thickness along its edge to provide a recess 9 and the fabric I creased or crimped at lll and l I before the slurry is applied thereto so that the fabric is permanently set along these lines without distorting any other portion of the fabric.

It has been found that prior methods of crimping the fabric have caused it to assume a distorted or arcuate form along certain longitudinal lines with the result that the combined action of the moisture from the wet gypsum, the pressure of the master rolls. the ironing of the boards, and the drying thereof causes the floor of the recess to assume an arcuate form, as indicated by the dotted line l2. Also, the surface of the board adjacent the depression assumes an arcuate form, as indicated by the dotted line i3. The finished board is, therefore, formed with undesirable longitudinal depressions and raised portions. This result is commonly referred to as cupping" and, although the distortion is not great, it is very noticeable and objectionable in a nished wall. The mechanism disclosed herein effectively obviates the above noted distortions and provides finished plasterboards in which the surfaces previously referred to are flat and parallel.

Fig. 3 is a somewhat diagrammatic side elevation of a machine for manufacturing the plasterboard shown in Fig. 1, and this machine comprises an elongated frame or table I4, which table may be of any suitable construction adapted to support the usual fabric strip forming the cover sheet 4 (Fig. 1).

The fabric is delivered onto the table in a continuously moving strip advancing in the direction of the arrow (Fig. 3). The fabric strip is tensioned by means of any suitable tensioning apparatus and the edges of the strip pass between the rolls of crimping devices Il. two of which are positioned adjacent each side of the path of the strip. The strip then moves under a suitable gypsum mixer IB and the wet gypsum is delivered to this strip and suitably distributed by means of a spout I1. The fabric edges l (Fig. 1) may then be automatically folded over the edge of the gypsum layer by the usual well-known folding devices and a backing fabric 8 is continuously delivered onto the wet gypsum. The assembled web then passes between so-called master rollers or pressure rolls I8 and Il. and may later be cut into lengths and delivered to a drying kiln. 'I'he so-called crimping devices I5 previously mentioned offset the edges of the fabric strip in the manner shown in Fig. 7. and the lower master roll I9 is provided with shoulders for supporting the offset margin. A groove 26 is provided adjacent each end of the master roll IB (Fig. 8) and a split ring 2| is secured therein by means of ush head screws 22. This ring is thicker than the depth of the groove 20 by the amount of offset desired in the fabric. Therefore, each marginal oilset portion of the fabric will be supported on the raised surface of one of these rings as the web passes between the master rolls. The combination of crimping devices which permanently crimp the paper without distortion of the parallel surfaces, with master rolls constructed to retain the fiat parallel relationship throughout all further manufacturing operations, is a very important feature of the present invention.

The machine is adjustable for the manufacture of plasterboard of different widths, and, therefore, one or more grooves 20a are provided, which grooves are of the same width and depth as the groove 20 so that the split ring 2i can be positioned in any one of the grooves in accordance with the width of the board to be manufactured. It will be understood that similar grooves and rings are provided on the master roll for each edge of the paper. A filler ring 2la is provided to fill the unused groove as illustrated. This filler ring is flush with the surface of the roller when the ring is secured in the groove.

Fig. 9 is a somewhat diagrammatic view of the master rolls and the roll scraping assembly used in connection therewith, the lower roll shaft and a part of the scraper frame being shown in section,

In order to provide a uniformly smooth surfaced plasterboard, it is desirable to keep the lower master roll I9 free from dirt and particularly free from small accumulations of gypsum slurry. Also, it is important that the assembled plasterboard web should be directed accurately to the surface of the lower master roll. so that there may be no distortion of the fabric either before or after entering between the rolls.

In the embodiment shown in Fig. 9, a frame 23 is pivoted at 2l in axial alignment with the lower roll i9. Arms 25 extend rearwardly from the pivotal axis and are provided with an upwardly extending cross member or bar 26 on which is mounted a plate 21, which plate forms an extension of the table I4 over which the fabric web moves as it passes to the master rolls. 'I'he leading edge of the plate 21 conforms snugly with the surface of the roll I9. so that the plasterboard web is accurately directed tangentially to the periphery of the 1'011.

The table Il is arcuately cut away at Ila so that the frame 2l and plate 21 thereon may be moved around the pivot 24 on which the frame is supported. The frame is provided with one or more downwardly extending arms I8 on each arm of which is suspended a weight 29 so that the plate Il is normally supported in alignment with the table Il and the surface of the associated roll Il. The rolls are usually spring-pressed so that they will yield to any unusual or accidental pressure and will return to normal position when this pressure is removed.

A scraper bla/de 3l is secured to the cross bar by means of bolts 3 l, which bolts pass through slots 32 (Fig. 10) in the blade so that the leading edge of the scraper blade may be adjusted snugly against the roll as shown in Fig. 9. The sharp scraping edge of the blade 30 is provided with notches 33 which are of sufficient size to provide clearance for the fabric-supporting rings 2l on the roll I8. It is obviously impractical to provide notches ll which' accurately llt whatever rings 2l are being used and yet it is equally desirable that the rings and closely adjacent portions of the roll should be scraped and kept free from accumulations of any material which would cause irregularities in the finished product. The blade or plate 3B is therefore provided with a sumcient number of notches or cutaway portions 33 to accommodate any ring or rings 2l which may be applied to the roll.

In order to scrape the face and sides of each ring 2| and the portions of the roll adjacent thereto, additional small scrapers 3l are removably mounted on the pivoted bracket 23 by means of clamping screws l! (Fig. 9) One of these ring scraper blades 3l is illustrated in Fig. 10 in diagrammatic working relationship with the main scraper It. The ring scraper is wider than its associated notch I3 in the main scraper 3d and is provided on one end with a notch 3B corresponding closely with the dimensions of the split ring Il, so that the notched end of the scraper conforms snugly with the contour of the ring and the adjacent surface of the roller I9.

One of these ring scrapers 34 is provided for each ring groove in the roller i9, and for each large diameter ring 2| which is mounted on the roller, the notched end 36 of a ring scraper is used forengaging the roller. Also, in each case where a filler ring Ila is used, the associated scraper Il is reversed, end for end, in its support so that the straight edge end 3l is in contact with the ring 2id and adjacent portions of the roller. By this means, whenever one ring is substituted for another in the roll, it is only necessary to loosen the clamping screws 35 and reverse the associated scraper plate 34.

The crimping units I5 previously mentioned are also adjustable to accommodate fabric strips of various widths. One of the crimping devices is illustrated in detail in Fig. 5 and comprises an elongated base plate 38 secured to the underside of the table M by means of bolts 39. This plate l! is provided with portions Ill (Fig. 6) extending upwardly into an opening 4I in the table i4 and forming V-ways to support a carriage I2 which latter is adapted for longitudinal adjustment on the base transversely of the table. The upper surface of the V-way portions Ill and the surface of the carriage l2 are substantially flush with the top of the table Il so that they do not interfere with movement of the fabric strip over the table. The carriage Il is provided with downwardly extending shaft-supporting blocks il and and in which a fixed shalt il is supported. Idler rollers 4l and 4'! are mounted for free rotation on the shaft Il and in closely adjacent relationship as shown. The upper surface of the roller is substantially flush with the surface of the table Il while the roller 4l is of larger diameter and projects above the table a distance conforming to the desired onset of the recessed plasterboard to be manufactured. The shaft 45 is provided with spacing collars 4l and 4G and the rollers and spacing collars are longitudinally adjustable on the shalt 4B by means of nuts Sil and Il, which latter are threaded on the shaft so as to provide for simultaneous longitudinal adjustment of both rollers on the shaft 4l.

Spaced flanges 52 project upwardly from the outer end of the carriage I2 and a block Il is pivoted at its outer end in the opening between the flanges by means of an eccentric pivot pin il. The partial rotary adjustment of this eccentric pivot pin 5l will raise or lower the pivot point of the block $3 for a purpose which will be described later. A stub shaft 55 is mounted in block 53 and extends parallel with the lower shaft I5. This shaft 55 is provided with a small diameter idler roller 56 complementary to the lower roller 6l and in alignment therewith, and a large dlameter idler roller 51 complementary to the lower roller 4B. The rollers may be provided with ball bearings as shown. The shaft 55 is also provided with the spacing collars 48a and a and with nuts 50a and Bla, all of which function in the same manner as previously described for spacing and adjusting the rollers on the shaft.

The pivoted block El is provided with a vertical thumb screw 58 threaded therethrough with its lower end in engagement with the carriage base so that the upper roller assembly is normally supported thereon. By adjusting this screw, the shaft 55 and rollers thereon may be angularly adjusted with respect to the pivot pin M so that the upper shaft and rollers may be adjusted into parallel relationship with the lower shaft and rollers thereon irrespective of the rotary position of the eccentric pivot pin El. These adjustments are desirable in order to accurately adjust the rollers to accommodate fabric of different thicknesses. The adjustable eccentric pivot pin 5I con.. trois the vertical height of the upper rollers, while the thumb screw 58 controls the adjustment to parallelism with the lower rollers.

The base plate 38 is provided adjacent its outer end with an upwardly extending lug 59 having a thumb screw 60 rotatably mounted therein. This thumb screw is threaded into the carriage as illustrated. so that the carriage may be longitudinally adjusted to conform with the width of the fabric strip being used. The relationship of the various crimping units l5 is shown in Fig. 4, and a plurality of these units in series is preferable in order to provide a more permanent crimp in the fabric. The fabric is crimped in the manner shown in Fig. 7, the rollers preferably being provided with rounded edges Bl, over which the fabric is crimped, as shown. The fact that the relationship of the diameter of the rollers one to the other is in accordance with the height of the crimp to be produced, and that the rollers are independently rotatable, prevents any ironing of the fabric surface and also prevents any distortion of the fabric except along the crimped lines. Therefore, the body of the fabric and the odset portion are perfectly parallel.

Apinllisremovablympportedinacomple- I4 secured thereto mentary hole in the carriage and when it is desired to eliminate the crimping process in order to manufacture non-recessed boards, the upper roller assembly may be raised to an angular position on the pivot 5l and the pin l2 may then be inserted through a hole 6l so that the upper assembly is supported thereon in its raised angular position,

It will be understood that the rollers may be spaced any desired distance on their respective shafts merely by inserting collars 4l and a of the required width.

The unit assembly just described provides cooperating stepped pressure rolls in which each step comprises independently rotatable pressure rollers with means for adjusting the pressure and angular relationship of the rolls.

As previously stated, the entire assembly may be adjusted by means of the thumb screw 86, so that the position of the lower roller 41 relative to the fabric web determines the required width of the flat oil'set margin of the fabric. Also the upper rollers may longitudinally be adjusted relative to the lower roller to determine the width of the intermediate crimped portion of the web. For instance, if the entire carriage shown in Fig. 5 is moved to the left by means of the adjusting screw 60, the width of the offset marginal portion of the fabric is decreased while the width of the intermediate crimped portion remains unchanged, conversely. if the upper rollers 56 and 51 only are moved to the right by means of the adjusting nuts 50a and Ela, then the width of the ini termediate crimped portion of the fabric is increased while the width of the offset marginal portion remains unchanged. The latter adjustment of the upper rollers and the consequent widening of the intermediate crimped portion ls illustrated by dotted lines in Fig. 7. It will be obvious that by suitable adjustment of the device, the crimped step in the fabric may be made as abrupt or as extended as required.

It is intended, of course. that the invention should not be limited to the specific embodiment or embodiments disclosed herein, since modications may be made, and it is contemplated, therefore, by the appended claims to cover any such modifications as fall within the true spirit and scope of this invention.

Having thus described this invention, what is claimed and desired to be secured by Letters Patent is:

l. In a machine for manufacturing recessed plasterboard. the combination with means for permanently crimping a continuously moving fabric web adjacent the edge thereof to provide a narrow marginal strip-like portion raised above but in a plane parallel with the main portion of said web and connected thereto by an offsetting narrow strip-like portion, said two strip-like portions together having an angular reinforcing cross-section, means to apply a layer of gypsum slurry to said web and strip-like portions, means to continuously apply a fabric backing web on said slurry, and means to apply transverse linear pressure to said continuously moving assembly. of means to ilxedly support said marginal strip portion in the said raised parallel relationship at the line of application of said pressure.

2. In a machine for manufacturing recessed plasterboard, the combination with means for permanently crimping a continuously moving fabric web adjacent the edge thereof to provide a nag-row marginal strip-like portion raised above but in a plane parallel with the main portion of said web and connected thereto by an o'setting narrow strip-like portion. said two strip-like portions together having an angular reinforcing cross-section, means to apply a layer of gypsum slurry to said web and strip-like portions, means forward of said crimping means to continuously apply a fabric backing web on said slurry, and a pair of co-operating rollers positioned to apply transverse line pressure to said continuously moving assembly to form recessed gypsum board web, of means on one of said rollers to continuously retain said marginal strip portion in the said raised parallel relationship immediately at said transverse pressure line.

3. In a machine for manufacturing recessed plasterboard, means for permanently crimping a continuously moving fabric web adjacent the edge thereof to provide a narrow marginal strip-like portion raised above but in a plane parallel with the main portion of said web and connected thereto by an oifsetting narrow striplike portion. said two strip-like portions together having an angular reinforcing cross-section, means forward of said crimping means to apply a layer of gypsum slurry to said web and strip-like portions, means to continuously apply a fabric backing web on said slurry. a pair of rollers between which said assembly continuously moves to apply suf iicient pressure to form a plasterboard web, the lower roller having an annular shoulder positioned to support said marginal strip portion in the said raised parallel relationship while said pressure is applied.

4. In a machine for manufacturing recessed piasterboard, means for permanently crimping a continuously moving fabric web adjacent the edge thereof to provide a narrow marginal striplike portion raised above but in a plane parallel with the main portion of said web and connected 40 thereto by an offsetting narrow strip-like portion,

said two strip-like portions together having an angular reinforcing cross-section. means forward of said crimping means to apply a layer of gypsum slurry to said web and strip-like portions, means to continuously apply a fabric backing web on said slurry, and a pair of co-operating pressure rollers respectively above and below said continuously moving assembly to form a plasterboard web, the lower roller having an annular groove positioned below said raised marginal portion, and an annular ring in said groove and of an outside diameter and contour to flxedly support said marginal portion in said raised parallel relationship at the line of pressure.

5. In a machine for making recessed plasterboard. a support for a continuously moving fabric web, means adjacent each side of said web for continuously offsetting an adjacent marginal strip-like portion out of the plane of said web lbut in a plane parallel therewith and connected thereto by an offsetting narrow strip-like portion, said two strip-like portions together having an angular reinforcing cross-section, means to adjust at least one of said offsetting means to accommodate a web of different width, a pair of transverse pressure rollers between which said assembly continuously passes to form pressed plasterboard, one of said rollers having annular grooves therein positioned to correspond with the marginal oifset portions of webs of different widths nd interchangeable annular rings in said grooves and at least flush with the surface of said roller, certain of said rings being of an outside diameter and contour suillcient to support said strip-iikemarginal portions in said oilet parallel relationship during continuous passage between said pressure rollers.

6. In a machine for making recessed plasterboard including a fabric web having at least one odset marginal strip-like edge, a pair of pressure rollers between which said web having a plaster layer and a cover fabric thereon continuously moves. a plurality of annular grooves in the bottom pressure roller, each groove being positioned in alignment with the offset marginal edge of a fabric oi' predetermined width, interchangeable rings in said grooves, at least one of said rings being of sufficient outside diameter to support said offset edge portion of said fabric in its normal oifset relationship to the surface of said roller, illler rings in the remaining grooves. an elongated scraper blade supported in `working relationship with said roller and having notches in its edge in alignment with each groove and each notch of sufficient size to provide clearance for one of said offset supporting rings, and a scraper in alignment with each ring, one end of said scraper having a notch snugly fitting the contour oi' an oil'set supporting ring and the adjacent roller surface.

7. A crimping device for a continuously moving fabric web for plasterboard cover sheets comprising two pairs of closely adjacent freely and independently rotatable rollers, all of said rollers having their axes in the same plane and each pair adapted to snugly engage said moving web therebetween but in different planes and means for passing said web between said pairs of rollers whereby said rollers are frictionally rotated by said web.

8. A crimping device for a continuously moving fabric web for plaster-board cover sheets comprising two pairs of closely adjacent freely and independently rotatable rollers, all of said rollers having their axes in the same plane and each pair adapted to snugly engage said moving web therebetween but in different parallel planes to provide a permanent offset crimp between said parallel planes and means for passing said web between said pairs of rollers whereby said rollers are frictionally rotated by said web.

9. In a crimping device for a continuously moving fabric web for plasterboard cover sheets, a pair of freely and independently rotatable pressure rollers in transverse alignment under, the path of said web, the web-contacting surfaces of said rollers being in stepped relationship. a pair of freely and independently rotatable pressure rollers above the path of said web and in complementary web-engaging stepped relation with said i'lrst pair of rollers, the axes of all of said rollers being in substantially the same vertical plane with respect to said web and means for passing said web between said pairs of rollers whereby said rollers are frictionally rotated by said web.

l0. In a crimping device for a continuously moving fabric web for plasterboard cover sheets, a pair of freely and independently rotatable rollers in transverse axial alignment under the path of said web, a pair of freely and independently rotatable pressure rollers above the path of said web and in complementary web-contacting relation with said first pair of rollers, the axes of all of said rollers being in substantially the same vertical plane, the rollers of each cio-operating fabric-contacting pair being of different diameter and each axially spaced from its axially aligned roller so that an offset crimp is provided in said web between said rollers, means to adjust the parallel spaced relation of said pairs of rollers and means for passing said web between said pairs of rollers whereby said rollers are frictionally rotated by said web.

ll. In a plasterboard manufacturing machine, means for continuously moving a fabric cover strip, a group of freely and independently rotatable pressure rollers for engaging a marginal portion of said strip therebetween, all of said rollers having their axes in the same vertical plane, said group comprising a pair of rollers in end-to-end relationship below the path of said fabric with their fabric-engaging surfaces out of alignment, and a pair of pressure rollers above the path of said fabric with their fabric-engaging surfaces in complementary stepped relationship to said first pair of rollers, the rollers of each pair being spaced to provide a predetermined offset permanent crimp in said fabric so that the offset marginal portion thereof is parallel with the body portion of said fabric and means for passing said fabric between said pairs oi rollers whereby said rollers are frictionally rotated by said fabric.

l2. In a machine for making recessed plasterboard including a. fabric web having at least one offset marginal strip-like edge, a pair of pressure rollers between which said web having a plaster layer and a cover fabric thereon continuously moves, a plurality of annular grooves in the bottom pressure roller, each groove being positioned in alignment with the odset marginal edge of a fabric web of predetermined width, interchangeable rings in said grooves, at least one of said rings being of sufficient outside diameter to support said offset edge portion of said fabric in its normal offset relationship to the surface of said roller, filler rings in the remaining grooves, and an elongated scraper blade supported in working relationship with said roller and having notches in its edge in alignment with each groove and each notch of suillcient size to provide clearance for one of said offset supporting rings.

13. A method for manufacturing recessed plasterboard which comprises crimping a continuously moving fabric web adjacent the edge thereof to provide a narrow marginal strip-like portion raised above but in a plane parallel with the main portion of said web, and connected thereto by an offsetting narrow strip-like portion, said two strip-like portions together having an angular reinforcing cross section, applying a layer of gypsum slurry to said web and strip-like portions, continuously applying a fabric backing web on said slurry,A applying transverse linear pressure to said assembly of said webs and slurry, and flxedly supporting said marginal strip portion in said raised parallel relationship to the line of application of said pressure.

14. A crimping device for a continuously moving fabric web for plaster-board cover sheets comprising two pairs of closely adjacent freely and independently rotatable rollers, all of said rollers having their axes in the same plane and each pair adapted to snugly engage said moving web therebetween but in different planes, and means for `passing said web between said pairs of rollers whereby said rollers are frictionally rotated by said web, at least one of said rollers being adinstable longitudinally of its axis to vary the width of the crimped portion.

15. In a machine for manufacturing recessed plasterboard, means for permanently crimping a continuously moving fabric web adjacent the edge thereof t0 provide a narrow marginal strip-like 6 escasas and engaged and driven by said strip-like portion with its strip-engaging portion above the general plane of the fabric web, and another freely rotatable idler roller above and engaged and driven by said strip-like portion with its strip-engaging portion opposite and parallel to the strip-engaging portion of the rst roller and engaged and driven by said strip-like portion.

RALPH H. HURD.

Certicate of Correction Patent NQ. 2,392,923.

RALPH H. HURD January 15, i946- It is hereby certified thaterror appears in the grinted specification of the above numbered atent requiring correction as foliows: D

are a pair" insert the words meensjorward of sazd osettmg means to apii claim 5, be

age 4, second column, line 65,

a le er o sum slurry to said web and stri -lzke portions meansfor applying e Q buckling egiygn said slur and that the salz Letters Patent should be read wit this correction therein that t e same may conform to the record of the case m the Patent Oce.

Signed and sealed this 23d day of April, A. D. 1946.

[sur] LESLIE FRAZEB,

First Assistant Uommamcr of Patents.

6 escasas and engaged and driven by said strip-like portion with its strip-engaging portion above the general plane of the fabric web, and another freely rotatable idler roller above and engaged and driven by said strip-like portion with its strip-engaging portion opposite and parallel to the strip-engaging portion of the rst roller and engaged and driven by said strip-like portion.

RALPH H. HURD.

Certicate of Correction Patent NQ. 2,392,923.

RALPH H. HURD January 15, i946- It is hereby certified thaterror appears in the grinted specification of the above numbered atent requiring correction as foliows: D

are a pair" insert the words meensjorward of sazd osettmg means to apii claim 5, be

age 4, second column, line 65,

a le er o sum slurry to said web and stri -lzke portions meansfor applying e Q buckling egiygn said slur and that the salz Letters Patent should be read wit this correction therein that t e same may conform to the record of the case m the Patent Oce.

Signed and sealed this 23d day of April, A. D. 1946.

[sur] LESLIE FRAZEB,

First Assistant Uommamcr of Patents. 

